MAVEN is operated by the University of Colorado at Boulder (CU Boulder) while MSL RAD is run by the Southwest Research Institute (SwRI) in Boulder, Colorado.

The solar storm occurred on September 11 and produced an aurora 25 times brighter than any ever seen by MAVEN, which has studied the interaction between Mars' atmosphere and the solar wind for three years.

"When a solar storm hits the Martian atmosphere, it can trigger auroras that light up the whole planet in ultraviolet light," stated MAVEN Imaging Ultraviolet Spectrograph team member Sonal Jain of CU Boulder's Laboratory for Atmospheric and Space Physics.

Scientists were surprised by the solar activity, which occurred at a time in the 11-year solar cycle that is usually quiet, on approach to solar minimum.

Several storms have recently erupted on the Sun's surface. The storm that produced the auroras on Mars was observed from Earth in spite of the fact that Earth and Mars are currently on opposite sides of the Sun.

On the Martian surface, NASA's Curiosity rover's RAD measured radiation levels twice as high as any detected since its 2012 landing.

"NASA's distributed set of science missions is in the right place to detect activity on the Sun and examine the effects of such solar events at Mars as never possible before," noted MAVEN Program Scientist Elsayed Talaat.

Radiation measurements by Curiosity's RAD are assisting scientists in assessing the planet's habitability as well as planning for the safety of future astronauts.

Strong solar storms like those in September significantly increase the level of radiation that comes through the Martian atmosphere to its surface. Interactions between this radiation and the atmosphere produce secondary particles from which astronauts will need shielding.

"If you were outdoors on a Mars walk and learned that an event like this was imminent, you would definitely want to take shelter, just as you would if you were on a space walk outside the International Space Station (ISS). To protect our astronauts on Mars in the future, we need to continue to provide this type of space weather monitoring there," said RAD Principal Investigator Don Hassler, also of SwRI Boulder.

Because Mars has no magnetic field, auroras produced by solar storms can cover the entire planet. On Earth, such auroras are usually confined to the polar regions.

Solar storms may also be responsible for the loss of Mars' atmosphere in the solar system's early years. Atmospheric loss is believed to be one of the reasons the planet changed from wet to dry.